JP4897071B2 - Optical glass - Google Patents

Description

  The present invention has a low glass transition temperature (Tg) and a high refractive index and low dispersibility, is excellent in chemical durability, particularly in ISO test method acid resistance, and has good internal transmittance and lens preform productivity. The present invention relates to an optical glass suitable for precision mold press molding.

  In general, there are a spherical lens and an aspheric lens as lenses constituting the optical system. Many spherical lenses are manufactured by grinding and polishing a glass molded product obtained by reheat press molding a glass material. On the other hand, an aspherical lens is obtained by press-molding a heat-softened lens preform material with a mold having a high-precision molding surface and transferring the shape of the high-precision molding surface of the mold to the lens preform material. The mainstream method is to manufacture by precision mold press molding.

  In order to obtain a glass molded product such as an aspherical lens by precision press molding, it is necessary to press mold in a high temperature environment as described above, so the mold used at this time is also exposed to high temperature, High press pressure is applied to the mold. Therefore, when the lens preform material is heat-softened and when the lens preform material is press-molded, the molding surface of the mold is oxidized or eroded, or a release film provided on the surface of the mold molding surface is provided. In many cases, a highly accurate molding surface of the mold cannot be maintained due to damage, and the mold itself is easily damaged. If it becomes such, it will be forced to replace | exchange a metal mold | die, the frequency | count of replacement | exchange of a metal mold | die will increase, and it will become difficult to implement | achieve low cost and mass production. Therefore, the glass used as the lens preform material for precision press molding suppresses the above damage, maintains a high-precision molding surface of the mold for a long time, and enables precision press molding with a low pressing pressure. In view of the above, it is desired to have a glass transition temperature (Tg) as low as possible.

  There are two types of methods for producing lens preform materials. One is a method in which the glass is directly produced from molten glass by a dropping method. The other is produced by grinding and polishing a processed product obtained by grinding a glass block into a reheat press or ball shape. In any method, when a molten glass is formed into a desired shape, a certain viscosity is required in order to obtain optical glass free from striae, devitrification, or little.

  When precision press molding is performed, the glass used as the lens preform material needs to have a mirror surface or a state close thereto. Optical glass for precision press molding generally has poor chemical durability, and when lens preform material is processed into a ball shape by grinding and polishing, it causes burns on the surface, making it impossible to maintain a mirror surface or a state close to a mirror surface. There is. In particular, the ISO test method acid resistance is an important characteristic among chemical durability.

  From the viewpoint of usefulness in optical design, an optical glass having a high refractive index is required, but there is a drawback that the transmittance is deteriorated.

  For the above reasons, there is a strong demand for optical glass having high refractive index and low dispersibility, low glass transition temperature (Tg), excellent ISO test acid resistance, high viscosity at liquidus temperature, and excellent transmittance. It has been.

In particular, there is a strong demand for an optical glass having a high refractive index and low dispersion having an optical constant in the range where the refractive index (n _d ) exceeds 1.85 and the Abbe number (ν _d ) is 36 or more.
Since high-refractive index and low-dispersion optical glass is very useful in optical design, various glasses have been proposed for a long time.

  JP-A-60-221338 and JP-A-62-100449 disclose optical glasses having a low glass transition point (Tg). The glasses specifically disclosed in these publications are described above. It does not meet the recent optical design requirements.

JP-A-8-217484, JP-A-2001-348244, and JP-A-2003-267748 specifically disclose optical glasses having optical constants within the above range. However, in the optical glass specifically disclosed in these publications, Ta ₂ O ₅ / Gd ₂ O ₃ is 1.9 or more and / or Ta ₂ O ₅ / (Y ₂ O ₃ + in mass ratio. (La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) does not satisfy 0.35 or more, so any or all of ISO test method acid resistance, internal transmittance, viscosity at liquidus temperature is insufficient It is.

WO 2004-54937 discloses an optical glass having a refractive index (n _d ) of 1.85 or more and a low glass transition point (Tg).

JP-A-60-221338 JP-A-62-100449 JP-A-8-217484 JP 2001-348244 A JP 2003-267748 A WO2004-54937

  The object of the present invention is to comprehensively eliminate the disadvantages found in the optical glass described in the background art, to have the optical constants described above, to have a low glass transition temperature (Tg), and to have excellent ISO test method acid resistance. An object of the present invention is to provide an optical glass having a high viscosity at a liquidus temperature, excellent transmittance, and suitable for precision mold press molding.

In order to solve the above-mentioned problems, the present inventor has conducted intensive test studies, and as a result, specific amounts of SiO ₂ , B ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , Ta ₂ O ₅ , Li ₂ O Including the above-mentioned optical constants, low glass transition temperature (Tg), excellent ISO test method acid resistance, high viscosity at liquidus temperature, excellent transmittance, suitable for precision press molding An optical glass was obtained.

In the first configuration of the present invention, the refractive index (n _d ) exceeds 1.85, the Abbe number (ν _d ) has an optical constant in the range of 36 or more, and SiO ₂ and B ₂ O _{3 are} essential components. An optical glass containing La ₂ O ₃ , Gd ₂ O ₃ , Ta ₂ O ₅ and Li ₂ O, substantially free of lead and arsenic components, and having a glass transition temperature (Tg) of 630 ° C. or lower. is there.

  According to the second configuration of the present invention, the water resistance of the powder method of the Japan Optical Glass Industry Association standard is Class 1 or Class 2, the acid resistance of the powder method is Class 1 to Class 3, and the ISO test method acid resistance is Class 1 to Class 4. It is an optical glass having the configuration 1 described above.

  The third configuration of the present invention is characterized in that the internal transmittance at a wavelength of 400 nm is 90.0% or more, and the logarithm log η of the viscosity η (dPa · s) at the liquidus temperature is 0.4 or more. 1 and 2 optical glasses.

  A fourth configuration of the present invention is the optical glass according to any one of the above configurations 1 to 3, wherein the liquidus temperature is 1160 ° C. or lower.

The fifth constitution of the present invention is the following formula expressed by the content by mass% on the oxide basis, Ta ₂ O ₅ / Gd ₂ O ₃ is 1.9 or more and / or Ta ₂ O ₅ / ( Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is 0.3 or more.

The sixth constitution of the present invention is the following formula expressed by the content in mass% on the basis of oxide, Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is 0.3 or more, and the total content of La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ and WO ₃ is 78%. The optical glass having the constitutions 1 to 5, which is as follows.

The seventh configuration of the present invention is the oxide based mass%,
SiO ₂ 0.1-8%,
B ₂ O ₃ less than 5-20%,
La ₂ O ₃ 15-50%,
Gd ₂ O ₃ 0.1-30%,
Ta ₂ O ₅ more than 10% up to 25%, and Li ₂ O 0.5% more than 3%,
Is an optical glass containing

According to an eighth configuration of the present invention, GeO ₂ 0 to 10% and / or Yb ₂ O ₃ 0 to 5% and / or TiO ₂ 0 to 1% and / or ZrO ₂ 0 to 10% are optional components. And / or Nb ₂ O ₅ 0-8%, and / or WO ₃ 0-10%, and / or ZnO 0-15%, and / or RO 0-10%, where RO is MgO, CaO, One or more selected from SrO and BaO, and / or Sb ₂ O ₃ 0 to 1%
And / or the total amount of fluorides substituted with part or all of one or more oxides of each of the above-mentioned metal elements contains each component in the range of 0 to 6%. It is the optical glass of the said structure 7.

The ninth configuration of the present invention is the oxide-based mass%,
SiO ₂ 0.1-8%,
B ₂ O ₃ less than 5-20%,
La ₂ O ₃ 15-50%,
Gd ₂ O ₃ 0.1-30% and Ta ₂ O ₅ more than 10% up to 25%,
Li ₂ O exceeding 0.5% and less than 3%,
And GeO ₂ 0-10% and / or Yb ₂ O ₃ 0-5% and / or TiO ₂ 0-1% and / or ZrO ₂ 0-10% and / or Nb ₂ O ₅ 0-8. % And / or WO ₃ 0-10% and / or ZnO 0-15% and / or RO 0-10%,
However, RO is, MgO, CaO, 1 kind or more selected from SrO and BaO, and / or Sb ₂ O ₃ 0~1%,
And / or the total amount of fluorides substituted with a part or all of one or more oxides of each of the above-mentioned metal elements contains each component in the range of 0 to 6%. It is the optical glass of the said structures 1-8.

According to a tenth configuration of the present invention, Lu ₂ O ₃ is contained in an amount of less than 0 to 0.5%, Y ₂ O ₃ is contained in an amount of less than 0 to less than 0.1%, and Al ₂ O ₃ is contained in an amount of 0 to 5%. 9 optical glass.

  The eleventh configuration of the present invention is a precision press-molding preform made of the optical glass of the above configurations 1-10.

  The twelfth configuration of the present invention is an optical element formed by precision press-molding the precision press-molding preform material of the above-mentioned configuration 11.

  A thirteenth configuration of the present invention is an optical element formed by precision press molding the optical glass of any one of the above configurations 1 to 10.

Glass optical glass of the present invention, the composition is _{SiO 2 -B 2 O 3 -La 2} O 3 -Gd 2 O 3 -Ta 2 O 5 -Li 2 O system, and that does not contain lead component, arsenic component Since the refractive index (n _d ) exceeds 1.85, the Abbe number (ν _d ) has an optical constant in the range of 36 or more, and the transition temperature (Tg) is 630 ° C. or less, the precision mold Suitable for press molding.

  Furthermore, since it is excellent in chemical durability, it is difficult to cause burns in grinding / polishing processing of lens preform materials and storage of lens preform materials. Further, since the liquidus temperature is low and the viscosity at the liquidus temperature is high, the stable productivity is excellent.

  Each component of the optical glass of the present invention will be described. Hereinafter, unless otherwise specified, the content of each component means mass%.

The SiO ₂ component is an indispensable component that is very effective in increasing the viscosity of the glass and improving devitrification resistance and chemical durability in the optical glass of the present invention. However, if the amount is too small, the effect is insufficient. If the amount is too large, the glass transition temperature (Tg) rises and the meltability deteriorates. Therefore, it can be contained preferably at 0.1%, more preferably 1%, most preferably 3% as the lower limit, preferably 8%, more preferably 6%, most preferably 5.5% as the upper limit. Can be contained.

SiO ₂ is introduced into the glass using, for example, SiO ₂ as a raw material.

The B ₂ O ₃ component is an indispensable component as a glass-forming oxide component in the optical glass of the present invention which is a lanthanum-based glass. However, when the amount is too small, the devitrification resistance is insufficient, and when the amount is too large, the chemical durability is deteriorated. Therefore, it is preferable to contain 5%, more preferably 6%, most preferably 8% as the lower limit, preferably less than 20%, more preferably 19.5%, most preferably 19% as the upper limit. can do.

B ₂ O ₃ is introduced into the glass using, for example, H ₃ BO ₃ or B ₂ O ₃ as a raw material.

The GeO ₂ component is a component having an effect of increasing the refractive index and improving the devitrification resistance. However, since the raw material is very expensive, the upper limit is preferably 10%, more preferably less than 4%, most preferably Preferably it can contain 2% as an upper limit.

GeO ₂ is introduced into the glass using, for example, GeO ₂ as a raw material.

The La ₂ O ₃ component is an indispensable component for the glass of the present invention, which is effective for increasing the refractive index and reducing the dispersion of the glass and has a high refractive index and low dispersion. However, when the amount is too small, it is difficult to maintain the value of the optical constant of the glass within the above range, and when it is too large, the devitrification resistance is deteriorated. Therefore, it may preferably contain 15%, more preferably 18%, most preferably 20% as the lower limit, preferably 50%, more preferably less than 47%, most preferably 45% as the upper limit. Can do.

La ₂ O ₃ is introduced into the glass using, for example, La ₂ O ₃ , lanthanum nitrate or a hydrate thereof as a raw material.

The Gd ₂ O ₃ component is effective for increasing the refractive index of the glass and lowering the dispersion. However, if the amount is too small, the above effects are not sufficient, and if the amount is too large, the devitrification resistance deteriorates. Therefore, it can be contained preferably at 0.1%, more preferably 0.5%, most preferably 1% as the lower limit, preferably 30%, more preferably less than 28%, most preferably 25%. It can contain as.

Gd ₂ O ₃ is introduced into the glass using, for example, Gd ₂ O ₃ as a raw material.

The Yb ₂ O ₃ component is effective in increasing the refractive index of the glass and lowering the dispersion. However, when it adds excessively, devitrification resistance will worsen. Therefore, the upper limit is preferably 5%, more preferably 4%, and most preferably 3.5%.

Yb ₂ O ₃ is introduced into the glass using, for example, Yb ₂ O ₃ as a raw material.

The TiO ₂ component has an effect of adjusting optical constants and improving devitrification resistance. However, if the amount is too large, the devitrification resistance deteriorates, and the internal transmittance at 400 nm also deteriorates. Therefore, the upper limit is preferably 1%, more preferably 0.8%, and most preferably 0.5%.

TiO ₂ is introduced into the glass using, for example, TiO ₂ as a raw material.

The ZrO ₂ component is an optional component having an effect of adjusting optical constants, improving devitrification resistance, and improving chemical durability. However, if the amount is too large, the devitrification resistance is deteriorated, and it is difficult to maintain the glass transition temperature (Tg) at a desired low value. Accordingly, the upper limit of the amount of this component is preferably 10%, more preferably less than 8%, and most preferably 7.5%. In particular, in order to easily obtain the above effect, the amount is more preferably 0.1% or more.

ZrO ₂ is introduced into the glass using, for example, ZrO ₂ as a raw material.

The Nb ₂ O ₅ component is an optional component that has an effect of increasing the refractive index and improving chemical durability and devitrification resistance. However, if the amount is too large, the devitrification resistance is deteriorated, and the internal transmittance at 400 nm is also deteriorated. Therefore, the upper limit is preferably 8%, more preferably 7%, and most preferably 6%.

Nb ₂ O ₅ is introduced into the glass using, for example, Nb ₂ O ₅ as a raw material.

The Ta ₂ O ₅ component is an indispensable component that has a remarkable effect of increasing the refractive index and improving chemical durability and resistance to devitrification. However, if the amount is too small, the effect is insufficient. If the amount is too large, it is difficult to maintain the optical constant in the above range. Therefore, it is possible to contain preferably more than 10%, more preferably 14%, most preferably more than 19% as a lower limit, preferably 25%, more preferably 24%, most preferably 23%. It can contain as.

Ta ₂ O ₅ is introduced into the glass using, for example, Ta ₂ O ₅ as a raw material.

The WO ₃ component has an effect of adjusting optical constants and improving resistance to devitrification. However, if the amount is too large, the devitrification resistance and the light transmittance in the short wavelength region of the visible light region are adversely affected. Therefore, the upper limit is preferably 10%, more preferably 8%, and most preferably 6%.

WO ₃ is introduced into the glass using, for example, WO ₃ as a raw material.

  The ZnO component has a large effect of lowering the glass transition temperature (Tg) and has an effect of improving chemical durability. However, if the amount is too large, the devitrification resistance deteriorates. Therefore, the upper limit is preferably 15%, more preferably 13%, and most preferably 10%. Moreover, in order to make especially easy to acquire the said effect, it is more preferable to make the quantity into 0.1% or more.

ZnO can be introduced into the glass using, for example, ZnO or ZnF ₂ as a raw material.

  The RO component (one or more components selected from MgO, CaO, SrO and BaO components) is effective in adjusting the optical constant. However, if the amount is too large, the devitrification resistance deteriorates. Accordingly, the upper limit is preferably 10%, more preferably 5%, and most preferably 3%.

  The RO component can be introduced into the glass using, for example, MgO, CaO, SrO, BaO or a carbonate, nitrate, hydroxide, or the like as a raw material.

The Li ₂ O component is an indispensable component because it has the effect of significantly lowering the glass transition temperature (Tg) and promoting the melting of the mixed glass raw material. However, if the amount is too small, the effect is insufficient. If the amount is too large, the devitrification resistance deteriorates rapidly and the chemical durability also deteriorates. Accordingly, it may preferably contain more than 0.5%, more preferably 0.6%, most preferably 1% as a lower limit, preferably less than 3%, more preferably 2.5%, most preferably It can contain 2% as an upper limit.

Li ₂ O can be introduced into the glass using, for example, Li ₂ O, Li ₂ CO ₃ , LiOH, LiNO ₃ or the like as a raw material.

The Sb ₂ O ₃ component can be optionally added for defoaming when the glass is melted. However, if the amount is too large, the transmittance in the short wavelength region of the visible light region is deteriorated. Accordingly, the upper limit is preferably 1%, more preferably 0.8%, and most preferably 0.5%.

The F component is effective for lowering the transition temperature (Tg) and improving the devitrification resistance while lowering the dispersion of the glass. In particular, the F component is allowed to coexist with the La ₂ O ₃ component. It has an optical constant within the range and has an effect of lowering the transition temperature (Tg).

  If the total amount of F as a substitute for a part or all of one or more oxides of each of the above metal elements is too large, the volatilization amount of the F component increases and it is difficult to obtain a homogeneous glass. Become. Therefore, the upper limit is preferably 6%, more preferably 5.5%, and most preferably 5%. In particular, in order to easily obtain the above effect, the amount is more preferably 0.1% or more.

  In this specification, the “oxide standard” means that oxides, composite salts, metal fluorides, etc. used as raw materials for the glass component of the present invention are all decomposed during melting and changed to oxides. The composition represents each component contained in the glass, with the total mass of the generated oxide being 100% by mass.

  In addition, the raw material used in order to introduce each component which exists in the said glass was described for the purpose of illustration, and is not limited to the said enumerated oxides. Therefore, it can be selected from known materials in accordance with various changes in the glass production conditions.

The present inventor adjusted the chemical durability and the internal transmittance at a wavelength of 400 nm by adjusting the content ratio of the Ta ₂ O ₅ component and the Gd ₂ O ₃ component to a predetermined value within the optical constants within the above range. It was found that the viscosity at the liquidus temperature is improved. That is, the value of Ta ₂ O ₅ / Gd ₂ O ₃ is preferably 1.9 or more, more preferably 2.2 or more, and most preferably 2.5 or more. Chemical durability refers to the powder method water resistance, powder method acid resistance, and ISO test method acid resistance of the Japan Optical Glass Industry Association standard, and particularly ISO test method acid resistance.

In addition, the present inventor, in the optical constant within the above range, the total of Ta ₂ O ₅ component content and Y ₂ O ₃ component, La ₂ O ₃ component, Gd ₂ O ₃ component and Yb ₂ O ₃ component content It has been found that chemical durability, internal transmittance at a wavelength of 400 nm, and viscosity at the liquidus temperature are improved by adjusting the ratio of the amounts to a predetermined value. That is, the value of Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is preferably 0.3 or more, more preferably 0.35 or more. Preferably, it is 0.4 or more.

Furthermore, in order to maintain a desired optical constant and maintain good weather resistance, the value of Ta ₂ O ₅ / Gd ₂ O ₃ , Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ + It is better to set the value of Gd ₂ O ₃ + Yb ₂ O ₃ ) within the predetermined preferred range at the same time.

In addition, when producing a high refractive index and low dispersion glass by the composition system of the present invention, as a result of earnest research to improve devitrification resistance, that is, stability during molding, La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ and WO ₃ , while keeping the upper limit of the total amount at a predetermined value, La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Y By adjusting the ratio of the Ta ₂ O ₅ content to the total amount of ₂ O ₃ to a predetermined value or more, an optical glass having a high refractive index, low dispersion and excellent stability was successfully produced.

Specifically, the upper limit of the total amount of La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ and WO ₃ is preferably 78% or less, more preferably The lower limit of Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) is preferably 0.3, while maintaining 75% or less, most preferably 73% or less. More preferably 0.35, and most preferably 0.4.

The devitrification resistance can be improved by adding a small amount of the Lu ₂ O ₃ component in the composition system of the present invention. Since the Lu ₂ O ₃ component has a remarkably high raw material price, when it is added excessively, the production cost becomes high and it becomes impractical, and there is a disadvantage that the devitrification resistance is deteriorated. Therefore, it can be contained preferably in an amount of less than 0.5%, more preferably 0.3%, and most preferably not contained.

The Al ₂ O ₃ component is effective in improving chemical durability. However, if the amount is too large, the devitrification resistance deteriorates. Therefore, the upper limit is preferably 5%, more preferably less than 4%, and most preferably 2%.

Each component of Hf ₂ O ₃ , SnO ₂ , Ga ₂ O ₃ , Bi ₂ O ₃ , and BeO can be included, but since Hf ₂ O ₃ and Ga ₂ O ₃ are expensive materials, the raw material costs are high. In actual production, SnO ₂ is high and is not realistic. When SnO ₂ is melted with a platinum crucible or a melting tank in which the portion in contact with molten glass is made of platinum, tin and platinum are alloyed. The alloyed parts have poor heat resistance, and there is concern about the danger of accidents in which holes are opened and molten glass flows out. Bi ₂ O ₃ and BeO have a harmful effect on the environment and have a negative impact on the environment. There is a problem that it is a very large component. Therefore, it can be contained preferably in an amount of less than 0.1%, more preferably 0.05%, and most preferably not contained.

Y ₂ O ₃ has a problem that the devitrification resistance is remarkably deteriorated. Therefore, it can be contained preferably in an amount of less than 0.1%, more preferably 0.05%, and most preferably not contained.

Next, components that should not be contained in the optical glass of the present invention will be described.
Lead compounds are components that are easy to fuse with molds during precision press molding and glass manufacturing, as well as glass processing such as polishing and environmental measures such as glass processing and glass disposal. The optical glass of the present invention should not be contained because it is necessary and has a problem that it is a component with a large environmental load.

Since As ₂ O ₃ , cadmium and thorium are harmful components to the environment and are very environmentally harmful components, they should not be contained in the optical glass of the present invention.

If P ₂ O ₅ is contained in the optical glass of the present invention, devitrification resistance is likely to be deteriorated, so it is not preferable to contain P ₂ O ₅ .

When TeO ₂ melts a glass raw material in a platinum crucible or a melting tank in which the portion in contact with the molten glass is formed of platinum, tellurium and platinum are alloyed, and the alloyed portion has poor heat resistance. Therefore, since there is concern about the danger of an accident that a hole is opened at that location and the molten glass flows out, it should not be included in the optical glass of the present invention.

  Furthermore, it is preferable that the optical glass of the present invention does not contain coloring components such as V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Eu, Nd, Sm, Tb, Dy, and Er. However, the term “not contained” means that it is not contained artificially unless it is mixed as an impurity.

  Moreover, since the composition of the glass composition of the present invention is expressed by mass%, it cannot be expressed directly in the description of mol%, but in the glass composition satisfying various properties required in the present invention The composition of each oxide present in terms of mol% generally takes the following values.

SiO ₂ 0.5~22%,
B ₂ O ₃ less than 10-40%,
La ₂ O ₃ 8-25%,
Gd ₂ O ₃ 0.1-15%,
More than 3% Ta ₂ O ₅ up to 9% and more than 2.5% Li ₂ O and less than 15%,
And GeO ₂ 0-15% and / or Yb ₂ O ₃ 0-2.5% and / or TiO ₂ 0-1% and / or ZrO ₂ 0-12% and / or Nb ₂ O ₅ 0 to 4%, and / or WO ₃ Less than six%, and / or 0 to 30% ZnO, and / or RO 0%, however, RO is one or selected from MgO, CaO, SrO and BaO 2 or more and / or Sb ₂ O ₃ 0 to 1%
In addition, the total amount as F of the fluoride substituted with one or more oxides of one or more of the above metal elements is 0 to 40%.

Next, the physical properties of the optical glass of the present invention will be described.
As described above, the optical glass of the present invention is preferably an optical constant having a refractive index (n _d ) of more than 1.85 and an Abbe number (ν _d ) of 36 or more from the viewpoint of usefulness in optical design. More preferably, the refractive index (n _d ) is greater than 1.85 and not more than 1.90, and the Abbe number (ν _d ) is in the range of 36 to 45, most preferably the refractive index. (N _d ) has an optical constant in the range of 1.851 to 1.89 and the Abbe number (ν _d ) in the range of 38 to 43.

  In the optical glass of the present invention, if the Tg is too high, as described above, when precision press molding is performed, deterioration of the mold tends to occur. Therefore, Tg of the optical glass of the present invention is preferably 630 ° C, more preferably 625 ° C, and most preferably 620 ° C.

  The yield point At is preferably 680 ° C, more preferably 675 ° C, and most preferably 670 ° C or less.

  When the chemical durability of the optical glass of the present invention is deteriorated, burns are likely to occur due to processing such as grinding and polishing, or even when storing lens preform materials or mold-pressed lenses. Therefore, the water resistance of the powder method of the Japan Optical Glass Industry Association standard is preferably class 2, more preferably class 1, the acid resistance of the powder method is preferably class 3-1, more preferably class 2-1, most preferably class 1. The acid resistance of the ISO test method is preferably class 4-1, more preferably class 3-1, more preferably class 2-1, most preferably class 1.

  The optical glass of the present invention is required to have excellent internal transmittance at 400 nm because light transmittance in the visible region is particularly important. Therefore, it is preferably 90% or more, more preferably 91% or more, and most preferably 92% or more.

  In the optical glass of the present invention, the liquidus temperature is preferably 1160 ° C. or lower in order to realize stable production by the following production method. More preferably, by setting it to 1140 ° C. or less, and particularly preferably 1120 ° C. or less, the viscosity range in which stable production is possible is widened, and the glass melting temperature can be lowered, so that energy consumed can be suppressed.

  The liquidus temperature means that a 30 cc glass sample is put in a platinum crucible and completely melted at 1250 ° C., cooled to a predetermined temperature and held for 1 hour, taken out of the furnace and immediately crystallized in the glass surface and glass. The lowest temperature at which no crystal is observed is observed. Here, the predetermined temperature represents a temperature set in increments of 20 ° C. from 1180 ° C. to 1000 ° C.

  As described above, the optical glass of the present invention can be used as a preform material for press molding, or the molten glass can be directly pressed. When used as a preform material, the production method and precision press molding method are not particularly limited, and known production methods and molding methods can be used. As a method for producing a preform material, for example, a glass gob forming method described in JP-A-8-319124, an optical glass manufacturing method described in JP-A-8-73229, and a preform material directly from molten glass such as a manufacturing apparatus are used. The strip material may be manufactured by cold working.

  In addition, when manufacturing a preform by dripping molten glass using the optical glass of the present invention, if the viscosity of the molten glass is too low, the glass preform is liable to get into striae. It becomes difficult to cut glass by tension.

  Therefore, for high quality and stable production, the logarithmic log η value of the viscosity η (dPa · s) at the liquidus temperature is preferably 0.4, more preferably 0.5, most preferably 0.6. Is the lower limit, preferably 2.0, more preferably 1.8, and most preferably 1.6.

  The precision press molding method of the preform is not particularly limited, and for example, a method such as a molding method of an optical element described in JP-B-62-41180 can be used.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
The composition of Examples (No. 1 to No. 5) of the glass of the present invention is made up of the refractive index (nd), Abbe number (νd), glass transition temperature (Tg), yield point (At), powder of these glasses. The results are shown in Table 1 together with the method water resistance RW (P), powder method acid resistance RA (P), ISO test method acid resistance SR, internal transmittance at 400 nm, liquid phase temperature and viscosity at the liquid phase temperature. In the table, the composition of each component is expressed in mass%.

  The optical glasses (No. 1 to No. 5) of the examples of the present invention shown in Table 1 are as shown in Table 1 for ordinary optical glass materials such as oxides, hydroxides, carbonates, nitrates and fluorides. Weigh, mix and mix into platinum crucibles for each composition shown in the examples, and melt, clarify, and stir at 1100-1500 ° C. for 3-5 hours depending on the meltability of the composition. After homogenization, it could be obtained by casting into a mold or the like and gradually cooling.

  Refractive index (nd) and Abbe number (νd) were measured for the optical glass obtained at a slow cooling rate of -25 ° C / hour.

Glass transition temperature (Tg) was measured by the method described in Japan Optical Glass Industry Society Standard ^{JOGIS08 -2003} (Measuring Method for thermal expansion of optical glass). However, a sample having a length of 50 mm and a diameter of 4 mm was used as a test piece.

  The yield point (At) was measured by the same measurement method as the glass transition temperature (Tg), and was set to a temperature at which the elongation of the glass stopped and the shrinkage started.

  The powder method water resistance RW (P) was performed according to the Japan Optical Glass Industry Association Standard “JOGIS06-1999”. Specifically, a glass crushed to a particle size of 425-600 μm is taken in a specific gravity gram, placed in a platinum bowl, and placed in a quartz glass round bottom flask containing pure water (pH 6.5-7.5). Then, it was treated in a boiling water bath for 60 minutes, and the weight loss (wt%) of the treated glass powder was calculated and classified according to the following classification method. When the weight loss rate is less than 0.05%, it is class 1, when it is 0.05% or more and less than 0.10%, it is class 2, and when it is 0.10% or more and less than 0.25%, it is class 3, 0.25%. When it is less than 0.60%, it is class 4, when it is less than 0.60% 1.10%, it is class 5, and when it is 1.10% or more, it is class 6.

  The acid resistance RA (P) by the powder method was performed according to the Japan Optical Glass Industry Association Standard “JOGIS06-1999”. Specifically, a glass crushed to a particle size of 425-600 μm is taken in a specific gravity gram, placed in a platinum bowl, put in a quartz glass round bottom flask containing a 0.01N nitric acid aqueous solution, and placed in a boiling water bath. It processed for 60 minutes, the mass loss (wt%) of the processed powder glass was computed, and it classified according to the following classification | category method. When the weight loss rate is less than 0.20%, class 1, when it is 0.20% or more and less than 0.35%, class 2, when it is 0.35% or more and less than 0.65%, class 3, 0.65% When it is less than 1.20%, it is class 4, when it is less than 1.20% 2.20%, it is class 5, and when it is 2.20% or more, it is class 6.

  The test method was performed according to ISO test method acid resistance “ISO8424: 1987 (E)”, and acid resistance SR was determined. Specifically, a glass sample of 30 mm × 30 mm × 2 mm whose six surfaces were polished as test pieces was suspended using a platinum wire in a predetermined solution at a temperature of 25 ° C., and was determined for a predetermined time (10 minutes, 100 Min, 16 hours, 100 hours). After the treatment, the weight loss of the sample is weighed, and the time required for eroding the glass layer having a thickness of 0.1 μm is calculated by the following formula. However, this calculation uses the value obtained by the minimum test time in which the mass loss per sample is 1 mg or more. If the weight loss does not exceed 1 mg even after 100 hours of treatment, the value at this time is used for calculation. When a nitric acid solution having a pH of 0.3 is used as the predetermined solution, the time required to corrode the 0.1 μm glass layer exceeds 100 hours, the grades 1 and 10 to 100 hours are grades 2, 1 to 10 The time was set to class 3, and 0.1 to 1 hour was set to class 4. If the time is less than 0.1 hour, use a pH 4.6 acetic acid buffer solution. If the time required to corrode the 0.1 μm glass layer exceeds 10 hours, class 5 or 1 to 10 hours 51, 1 to 0.1 hours were classified as class 52, and less than 0.1 hours were classified as class 53. In the ISO test method, a more detailed number is assigned depending on the state of change of the glass surface after the treatment, but it is omitted in this specification.

t _0.1 = t _e · d · S / ((m ₁ −m ₂ ) · 100)
t _0.1 : Time required for eroding the glass layer of _0.1 μm (h)
t _e : Processing time (h)
d: Specific gravity S: Surface area of the sample (cm ² )
m ₁ -m ₂ : Mass reduction amount of the sample (mg)

The internal transmittance was calculated from the transmittance including the reflection loss of samples having a thickness of 10 mm and 50 mm using the following equation. The internal transmittance was calculated with a thickness of 10 mm.
τ = exp [{ln (T2 / T1) / (t2-t1)} × l]
τ: Internal transmittance T2: Transmittance including reflection loss of sample with thickness 10 mm T1: Transmittance including reflection loss of sample with thickness 50 mm t2: Sample thickness 10 mm
t1: Sample thickness 50mm
l: 10 mm

  The liquidus temperature means that a 30 cc glass sample is put in a platinum crucible and completely melted at 1250 ° C., cooled to a predetermined temperature and held for 1 hour, taken out of the furnace and immediately crystallized in the glass surface and glass. The lowest temperature at which no crystal is observed is observed. Here, the predetermined temperature represents a temperature set in increments of 20 ° C. from 1180 ° C. to 1000 ° C.

  The viscosity of the glass was measured by the ball pulling method. Using the viscosity-temperature curve, the viscosity at the liquidus temperature was determined.

As can be seen from Table 1, all the optical glasses (No. 1 to No. 5) of the examples of the present invention have optical constants (refractive index (n _d ) and Abbe number (ν _d )) within the above range. In addition, since the glass transition temperature (Tg) is 630 ° C. or less, it is suitable for precision mold press molding, and further, the chemical resistance to powder method water resistance, powder method acid resistance, and ISO test method acid resistance is good. The liquid phase temperature and the logarithm log η of the viscosity at the liquid phase temperature are within the above range, so that stable productivity is possible.

Claims (10)

The refractive index (n _d ) exceeds 1.85, the Abbe number (ν _d ) has an optical constant in the range of 40 or more, and SiO _{2 is} 3 to 8% by mass% based on oxide as an essential component, B ₂ O ₃ 5-19.5%, La ₂ O ₃ 15-50%, Gd ₂ O ₃ 0.1-25%, Ta ₂ O _{5 over} 10% 25%, WO ₃ 1.5-6%, TiO It is an optical glass having _{20 to 1} %, ZnO 0.1% or more, containing Li ₂ O, substantially free of lead components and arsenic components, and having a glass transition temperature (Tg) of 630 ° C. or lower. The total content of La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ and WO ₃ is 73% or less, and at the liquidus temperature viscosity η (dPa · s) of the logarithmic logη is not less than 0.8, the optical glass has a liquidus temperature of 1100 ° C. or less.   The optical glass according to claim 1, wherein the water resistance of the powder method of the Japan Optical Glass Industry Association standard is Class 1 or Class 2, the acid resistance of the powder method is Class 1 to Class 3, and the acid resistance of ISO test method is Class 1 to Class 4.   2. The optical glass according to claim 1, wherein the internal transmittance at a wavelength of 400 nm is 90.0% or more. The following formula expressed by the content by mass% on the basis of oxide, Ta ₂ O ₅ / Gd ₂ O ₃ is 1.9 or more and / or Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ The optical glass according to claim 1, wherein + Gd ₂ O ₃ + Yb ₂ O ₃ ) is 0.3 or more. The value of Ta ₂ O ₅ / (Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ ) expressed by the content in mass% based on the oxide is 0.3. It is the above, The optical glass of Claim 1 characterized by the above-mentioned. % By mass based on oxide,
SiO ₂ 3-8%,
B ₂ O ₃ 5 to less than 19.5%,
La ₂ O ₃ 15-50%,
Gd ₂ O ₃ 0.1-25%,
Ta ₂ O ₅ exceeding 10% to 25%,
Li ₂ O exceeding 0.5% and less than 3%,
WO ₃ 1.5-6%,
ZnO 0.1-15%,
GeO ₂ 0-10% and / or Yb ₂ O ₃ 0-5% and / or TiO ₂ 0-1% and / or ZrO ₂ 0-10% and / or Nb ₂ O ₅ 0-8% And / or RO 0 to 10%, where RO is one or more selected from MgO, CaO, SrO and BaO, and / or Sb ₂ O ₃ 0 to 1%
And / or the total amount of fluorides substituted with part or all of one or more oxides of each of the above-mentioned metal elements contains each component in the range of 0 to 6%. The optical glass according to claim 1. The optical glass according to claim 1, comprising Lu ₂ O ₃ in an amount of less than 0-0.5%, Y ₂ O ₃ in an amount of less than 0-0.1%, and Al ₂ O ₃ in an amount of 0-5%. .   A precision press-molding preform comprising the optical glass according to claim 1.   An optical element formed by precision press-molding the precision press-molding preform according to claim 8.   An optical element formed by precision press-molding the optical glass according to claim 1.